Feature and flux of nutrient cycling in rubber plantation

Rubber plantations are one of the most successful types of artificial forests.The flux and characteristic parameters of 3 cycling nutrient elements(N,P,K) were studied in a rubber(Hevea brasiliensis) plantation of Clone PR107 at different ages.The results show that:(1) The flux of nutrients were found to increase with the age of the growth,which ranged as NKP.The total nutrient absorption,retention,return and nutrient of rubber latex in rubber plantation ecosystem were estimated to be 315.28-949.13kg·hm-2·a-1,282.78-714.51kg·hm-2·a-1,32.50-205.74kg·hm-2·a-1 and 10.18-37.73kg·hm-2·a-1.The nutrient input and output in soil ranged from 111.73kg.hm-2.a-1 to 652.79kg·hm-2·a-1,and 315.28kg·hm-2·a-1 to 949.13kg·hm-2·a-1,and the loss of nutrient in soil was just-249.94 kg·hm-2·a-1;(2) Characteristic parameters of nutrient cycling changed with increasing age.Both absorption and return coefficients increased,retention coefficient decreased,and soil and litter nutrient equilibrium index declined as well after 6 years.The litter decomposition limited the rate of nutrient cycling,which resulted in nutrient imbalance in the soil.Nutrient utilizing efficiency was reduced after the first growth up to 14 years;(3) There were differences of the characteristic parameter of nutrient cycling for each element.Absorption and return coefficient both ranked in the following order:NPK,retention coefficient and nutrient utilizing efficiency followed the sequence KPN and PKN,but the soil and litter equilibrium index stood in the order of PNK and KNP.It's also indicated that the liquidity of elements were the largest in N,second in K,and least in P,and so were the cycling rate and level.